Question

我必须为TCP Client / Server编写java项目。代码的目标是客户端向服务器询问文件。如果该文件可用，它将被保存到客户端目录中，并显示找到并保存文件的消息，否则找不到该文件。

当文件在Server目录中并且它将保存在客户端目录中时代码有效但如果文件不可用，它将在服务器端显示该文件不可用的消息但在客户端它将保存一个新的空文件，其中包含不可用的文件名，并向文件接收消息

你能帮忙吗

我有服务器代码

import java.io.*;
import java.net.*;
import java.util.*; 

//********************
public class Server
{
   static ServerSocket  ServSock;
   static int           QLen = 6;

   //***
   public static void main(String args[])
   {
      try
      {
         //*** establish server socket
         ServSock = new ServerSocket(Integer.parseInt(args[0]), QLen);

         while (true)
         {
               //***  accept a client
               Socket Sock = ServSock.accept();

               //*** pass the client to a new thread
               new Worker(Sock).start();
          }
      }
      catch(IOException e)
          {System.out.println(e);}
    }
}





//*************************
class Worker extends Thread
{
   Socket          Sock;
   PrintWriter     PW;
   BufferedReader  DIS;
   String          Question = "Enter the file name to transfer from server:";


   //**************
   Worker(Socket S)
   {Sock=S;}


   //**************
   public void run()
   {
     try
     {
        //*** thread identifies itself
        System.out.println("Thread: " + getName());


        //*** auto-flush
        //*** set up socket I/O streams
        PW = new PrintWriter (new BufferedWriter (new OutputStreamWriter(Sock.getOutputStream())),true);
        DIS  = new BufferedReader (new InputStreamReader (Sock.getInputStream()));



        //*** send server question
        PW.println(Question);


        //*** wait for client response
        String R = DIS.readLine();
        Scanner in = null; 
         try{
                BufferedOutputStream put=new BufferedOutputStream(Sock.getOutputStream());
                 BufferedReader st=new BufferedReader(new InputStreamReader(Sock.getInputStream()));
                  String str = "/Users/Batool/Desktop/HW/Server/";
                 String path = str + R; 
                 System.out.println("The requested file is path: "+path);
                 System.out.println("The requested file is : "+R);

                 File f=new File(path);
                  System.out.println(f.isFile());


                 if(f.isFile())
                 { 

            //System.out.println("inside if");

                     FileInputStream fis=new FileInputStream(f);
             System.out.println("File transfered");
System.out.println("———————————————————————————————");

                   byte []buf=new byte[1024];
                     int read;


                     while((read=fis.read(buf,0,1024))!=-1)
                     {
                         put.write(buf,0,read);
                         put.flush();
                     }




        }//end if 



                else{ System.out.println("File not found");
              System.out.println("———————————————————————————————");}//end else   

            }//end try


         catch(FileNotFoundException e)
            {
               System.out.println(e.getMessage());
               //System.exit(0);

             }//end catch


        //*** close this socket connection
        Sock.close();
        }

     catch(IOException e)
        {System.out.println(e);}
   }
}

我有客户端代码

import java.io.*;
import java.net.*;
import java.util.*; 

public class Client
{
   static Socket          sock;
   static PrintWriter     pw;
   static BufferedReader  br;
   static String          response = "";

   //************************************
   public static void main(String args[]) throws IOException
   {
      //*** establish connection to remote server
      sock = new Socket(args[0],
                       Integer.parseInt(args[1]));  //*** provide server name & port


      //*** set up socket I/O streams
      pw = new PrintWriter (new BufferedWriter (new OutputStreamWriter(sock.getOutputStream())),true);
      br  = new BufferedReader (new InputStreamReader (sock.getInputStream()));


      //*** wait for server question
      String r = br.readLine();    //*** THIS IS A BLOCKING CALL
      System.out.println("Server asks: " + r);

      //*** respond to server
      /*Scanner in = new Scanner(System.in); 
     String s = in.nextLine();
      pw.println(s);
      pw.flush(); 
     */
     Socket s=null;
        BufferedInputStream get=null;
        PrintWriter put=null;
        try
        { 
             get=new BufferedInputStream(sock.getInputStream());
            put=new PrintWriter(sock.getOutputStream(),true);

            String f;
            int u;
            //System.out.println("Enter the file name to transfer from server:");
            DataInputStream dis=new DataInputStream(System.in);
            f=dis.readLine();
            put.println(f);
            File f1=new File(f);
            String str = "/Users/Batool/Desktop/HW/Client";
            FileOutputStream  fs=new FileOutputStream(new File(str,f1.toString()));

        System.out.println(new File(str,f1.toString()));

System.out.println(f1.isFile());

            byte jj[]=new byte[1024];

            while((u=get.read(jj,0,1024))!=-1)
            { 
                fs.write(jj,0,u);
            } 
            fs.close();
            System.out.println("File received");
System.out.println("———————————————————————————————");
             sock.close();
        }catch(Exception e)
        {
                       System.out.println("File not found");
            System.out.println("———————————————————————————————");
            e.printStackTrace();
            System.exit(0);
        }


      //*** close this socket connection
      //sock.close();
   }
}

Answer 1

基本上您需要实施协议。

客户端询问服务器：你有文件X吗？

a）服务器说：是的，我得到了xyz字节，而md5sum是zyx

然后你的客户要求提供文件;它可以验证它获得了正确的字节数，并且发生了 no 传输错误。（当然你不需要那个验证部分;但根据你的背景，那些你应该考虑的东西也是如此）

b）服务器说：不，我没有那个文件

然后您的客户端会向其用户发送错误消息。

换句话说：服务器只是读取文件并推出字节不行！

您希望将服务器转换为提供服务的内容。并且服务具有合同，例如“输入”和“输出”。服务需要“协商”下一步应该发生的事情。在您当前的解决方案中，发生的所有事情都是硬编码的 - 这意味着已经有协议，但该协议是由您放入代码的指令定义的！

如果服务器没有使用java

1 个答案: